KR20110042259A - High energy lithium ion secondary batteries - Google Patents

Abstract

The present invention relates to a lithium ion secondary battery having a high total energy, energy density and discharge specific capacity when cycling at room temperature and at an intermediate discharge rate. Advanced batteries are based on high loadings of positive electrode materials with high energy capacity. This capacity can be loaded into the electrode at high density without sacrificing performance and is achieved through the development of a positive electrode active material having a very high specific energy capacity. Polymeric binders having an average molecular weight of at least 800,000 atomic weight units are used to facilitate high loading of the positive electrode material in the battery.

Description

High energy lithium ion secondary battery {HIGH ENERGY LITHIUM ION SECONDARY BATTERIES}

Cross Reference of Related Application

This patent application discloses US Patent Application Serial No. 12 / 403,521, co-pending to Buckley et al. Entitled “High Energy Lithium Ion Secondary Batteries” (March 13, 2009). And US Patent Application Serial No. 61 / 124,407 (filed April 16, 2008) to Buckley et al., Entitled " High Energy Lithium Ion Secondary Batteries. &Quot; It is claimed as a basic application of priority claims, and these applications are incorporated herein by reference.

Field of invention

The present invention relates to a lithium ion secondary battery having a high energy positive electrode material in a battery arrangement which provides a particularly high discharge energy density to the resulting battery. The invention also relates to a method of forming a high energy lithium ion secondary battery.

Lithium batteries are widely used in consumer electronics because of their relatively high energy density. Rechargeable batteries are also referred to as secondary batteries, and lithium ion secondary batteries generally have a negative electrode material that intercalates lithium. For some batteries currently in use, the negative electrode material may be graphite and the positive electrode material may include lithium cobalt oxide (LiCoO ₂ ). In practice, as only about 50% of the theoretical capacity of the cathode, for example only about 140 milliamp hours / g (mAh / g) can be used. Two or more other lithium-based cathode materials are also currently in use. Two such materials are LiMn ₂ O ₄ with spinel structure and LiFePO ₄ with olivine structure. Such other materials do not provide any significant improvement in energy density.

Lithium ion batteries are generally classified into two classes based on their use. The first class is a class in which lithium ion battery cells carry high power batteries and are designed to carry high currents (amps) for applications such as power tools and hybrid electric vehicles. However, by design, such battery cells lower energy because they generally provide high current but the structure reduces the overall energy that can be delivered from the cell. The second class of designs involves low energy for applications such as mobile phones, laptop computers, electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs), in which lithium ion battery cells carry higher total energy with high energy cells. To intermediate currents (amps).

Summary of the Invention

In a first aspect, the present invention provides a lithium ion secondary comprising a positive electrode comprising a positive electrode active material and a binder, a negative electrode comprising a first lithium intercalation composition, an electrolyte comprising lithium ions, and a separator between the positive electrode and the negative electrode It is about a battery. In some embodiments, the battery has a discharge energy density of about 240 Wh / kg or more when discharged from 4.6 V to 2.0 V. The positive electrode active material of the battery positive electrode comprises a second lithium intercalation composition. The positive electrode of the battery may comprise at least about 92% by weight positive electrode active material. The positive electrode active material comprises a second lithium intercalating composition represented by the formula xLiMO ₂ · (1-x) Li ₂ M'O ₃ , wherein M is one or more trivalent metal ions and one or more metal ions is Mn ^{+ 3} , Co ⁺³ or Ni ⁺³ , M 'represents one or more metal ions having an average valence of +4, where 0 <x <1. In some embodiments, the second lithium intercalation composition may further comprise from about 0.1 mol% to about 10 mol% metal fluoride as a coating. In a further embodiment, the positive electrode of the battery may comprise about 0.1 to 5 wt% of the electrically conductive material and about 0.5 to 7.9 wt% of the polymeric binder separately from the second lithium intercalation composition. This polymeric binder may include a polymer having an average molecular weight of at least about 800,000 atomic weight units. In some embodiments, the negative electrode of the battery has a thickness of about 65 microns to about 200 microns on the cross section of the current collector. In further embodiments, the battery may have a discharge energy density of at least about 250 Wh / kg to 550 Wh / kg. The battery may have a volumetric discharge energy density of at least about 550 Wh / l.

In a second aspect, the invention provides a lithium ion secondary battery comprising a positive electrode, a negative electrode comprising a first lithium intercalation composition, and a separator between the positive electrode and the negative electrode, wherein the positive electrode comprises at least about 92% by weight of a positive electrode active material, about 0.1 Lithium ion secondary battery comprising -5 wt% electrically conductive material and about 0.5-7.9 wt% polymer binder. In some embodiments, the positive electrode active material of the battery comprises a second lithium intercalation composition represented by the formula xLiMO ₂ · (1-x) Li ₂ M'O ₃ , wherein M is one or more trivalent metal ions, At least one metal ion is Mn ⁺³ , Co ⁺³ or Ni ⁺³ , and M 'represents at least one metal ion having an average valence of +4, where 0 <x <1. Any fluorine dopant may optionally substitute up to about 1 atomic percent oxygen in the formula of the second lithium intercalation composition. The positive electrode of the battery has a density of about 2.5 g / ml or more. In some other embodiments, the second lithium intercalation composition is represented by the formula Li _{1 + x} Ni _α Mn _β Co _γ O ₂ , wherein x ranges from about 0.05 to about 0.25 and α is from about 0.1 to about 0.4 Β is in the range of about 0.4 to about 0.65, and γ is in the range of about 0.05 to about 0.3. In some embodiments, the positive electrode material may further comprise from about 1.0 mol% to about 10 mol% metal fluoride as a coating. In one embodiment, the metal fluoride coating comprises AlF ₃ . In some embodiments, the second lithium intercalation composition of the positive electrode active material is represented by the formula Li _{1 + x} Ni _α Mn _β Co _γ M ″ _δ O _{2 -z / 2} F _z , wherein x is about 0.05 to about 0.25 Α is in the range of about 0.1 to about 0.4, β is in the range of about 0.4 to about 0.65, γ is in the range of about 0.05 to about 0.3, δ is in the range of about 0 to about 0.1, and z is In the range from about 0 to about 0.1, and M ″ is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, or a combination thereof. The negative electrode of the battery may comprise graphite, synthetic graphite, hard carbon, graphite coated metal foil, coke or combinations thereof. In some embodiments, the separator of the battery comprises polyethylene, polypropylene, ceramic-polymer composites or combinations thereof. Specifically, the separator may comprise a triple layer membrane of polyethylene-polypropylene-polyethylene. In addition, the electrically conductive material of the positive electrode may include graphite, carbon black, metal powder, metal fibers or combinations thereof. In some embodiments, the polymeric binder of the positive electrode is polyvinylidene fluoride (PVDF), polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylate, ethylene- (propylene-diene monomer) copolymer (EPDM) And mixtures and copolymers thereof. In connection with the structure, the battery may comprise a plurality of electrodes each having a polarity separated by a separator in the casing. In some embodiments, the electrodes and separators of the battery may be stacked, gel-rolled, or folded inside the casing. In general, the casing of a battery includes a polymer film, a metal foil, a metal can, or a combination thereof. For example, the casing of the battery may be prismatic or cylindrical. In some embodiments, the battery described herein has a discharge energy density of at least about 250 Wh / kg when discharged from 4.6 V to 2.0 V.

In a third aspect, the present invention relates to a method of forming a lithium ion secondary battery. The method includes assembling a positive electrode, a negative electrode, and a separator to form a battery having a discharge energy density of about 240 Wh / kg or more. The separator is inserted between the positive and negative electrodes of the battery, the positive electrode comprising a positive electrode active material including a binder and a lithium intercalation composition. The anode density is at least about 2.5 grams / milliliters (g / ml). In some embodiments, the positive electrode of the battery is formed by coating a positive electrode active material with a binder on a current collector. The positive electrode may comprise at least about 92% by weight of a positive electrode active material, wherein the lithium intercalation composition is represented by the formula xLiMO ₂ · (1-x) Li ₂ M'O ₃ , where M is one or more trivalent metal ions , At least one metal ion is Mn ⁺³ , Co ⁺³ or Ni ⁺³ , and M 'represents at least one metal ion having an average valence of +4, where 0 <x <1. The current collector of the battery positive electrode may include a metal foil, a metal grid, an expanded metal, or a metal foam. In a further embodiment, the current collector of the battery positive electrode comprises nickel, aluminum, stainless steel, copper or a combination thereof. In some embodiments, the positive electrode of the battery further comprises about 0.1-5 wt% of the electrically conductive material and / or about 0.5-7.9 wt% of the polymeric binder. The binder of the battery positive electrode may include a polymer having an average molecular weight of at least about 800,000 atomic weight units. In further embodiments, the negative electrode has a thickness of about 65 microns to about 200 microns on the cross section of the current collector. In some embodiments, the battery has a discharge energy density of at least about 250 Wh / kg when discharged from 4.6 V to 2.0 V.

In a fourth aspect, the present invention relates to a lithium ion secondary battery comprising a positive electrode, a negative electrode including a first lithium intercalation composition, and a separator between the positive electrode and the negative electrode. The positive electrode may comprise from about 92% by weight or more of the positive electrode active material, from about 0.1 to 5% by weight of the electrically conductive material, and from about 0.5 to 7.9% by weight of a polymeric binder comprising PVDF with an average molecular weight of at least about 800,000 atomic weight units.

Brief description of the drawings

1 is a schematic view of a battery structure separated from a container.

FIG. 2 is a first cycle charge / discharge voltage versus specific capacity curve of the battery described in Example 1, which is cycled at a discharge rate of C / 10 within a voltage range of 2.0 to 4.6 V. FIG.

3 is a specific capacity versus life curve for the battery of FIG. 2 showing a variation of discharge capacity as a function of cycle number.

4 is a first cycle charge / discharge voltage versus specific capacity curve of the coin-type battery battery described in Example 2, which is cycled at a discharge rate of C / 10 within a voltage range of 2.0 to 4.6 V. FIG.

5A is a front photograph of a pouch-type battery battery constructed in Example 3. FIG.

5B is a photograph of the side of a pouch-type battery battery constructed in Example 3. FIG.

5C is a discharge curve of the pouch-type battery battery constructed in Example 3. FIG.

Detailed description of the invention

Lithium ion batteries having the structures described herein exhibit not only high high overall energy but also high high energy densities, which are particularly suitable for low to medium speed applications. Such batteries also have good cycling characteristics that allow high energy values to be advantageously used over a significant time. Advanced batteries are based, in part, on anode materials with high energy capacities. The battery structure described herein that advantageously uses such a high energy capacity positive electrode material is provided to realize the highly high energy described herein. Specifically, this battery structure may comprise a very high loading of the positive electrode active material. The development of synthetic methods to realize positive electrode active materials with high tap density provides a suitable material for realizing the high loadings described herein for positive electrodes. In addition, very high loading of the positive electrode active material may be facilitated through the use of a polymeric binder having, at least in part, a molecular weight of at least about 800,000 AMU. The corresponding method of forming a battery cell is described. Moreover, the positive electrode active material may be coated or doped with an inorganic fluoride composition or coated and doped to improve the cycling characteristics of the cell at high energy density. In particular, inorganic coatings that provide improved cycling performance may also improve or at least not significantly reduce the overall energy density of both electroactive materials, although the weight of the coating does not directly contribute to capacity.

Lithium has been used in both primary and secondary batteries. An attractive feature of lithium metal is the fact that it is a light weight and the largest positive metal, and aspects of that feature also allow it to be advantageously captured in lithium ion batteries. Certain forms of metals, metal oxides and carbon materials are known to incorporate lithium ions into their structure through intercalation or similar mechanisms. Preferably the mixed metal oxides are further described herein as acting as an electroactive material for the positive electrode in secondary lithium ion batteries. Lithium ion batteries are referred to as batteries in which the negative electrode active material is also a lithium intercalation material. When lithium metal itself is used as anode or negative electroactive material, the resulting battery is generally referred to simply as lithium battery.

As used herein, the positive electrode active material includes a lithium intercalation metal oxide composition. In some embodiments, the lithium metal oxide composition may comprise a lithium rich composition that is generally believed to form a layered composite structure. In some embodiments, the positive electrode of the battery may comprise at least about 92% by weight of a positive electrode active material, the positive electrode active material comprises a composition represented by the formula xLiMO _2. (1-x) Li ₂ M'O ₃ , Wherein M is at least one trivalent metal ion, at least one metal ion is Mn ⁺³ , Co ⁺³ or Ni ⁺³ , and M 'represents at least one metal ion with an average valence of +4, where 0 <x < 1 Such materials may optionally have from about 0.1 mol% to about 10 mol% metal fluoride as fluorine dopants and / or coatings for oxygen substitution. The positive electrode of the battery may further comprise about 0.1 to about 5 weight percent of electrically conductive material and about 0.5 to about 7.9 weight percent of a polymeric binder.

In some embodiments, the negative electrode of the battery may have a thickness of about 65 microns to about 200 microns on the cross section of the current collector. The negative electrode of the battery may comprise graphite, synthetic graphite, hard carbon, graphite coated metal foil, coke or combinations thereof. The separator of the battery may comprise polyethylene, polypropylene, ceramic-polymer composites or mixtures thereof. Specifically, the separator may be a polyethylene-polypropylene-polyethylene triple layer membrane. The electrically conductive material of the anode may comprise graphite, carbon black, metal powder, metal fibers, or combinations thereof.

In general, the polymeric binder can be used to attach the powder together to the positive electrode as an integral structure. The polymeric binder of the positive electrode is polyvinylidene fluoride (PVDF), polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylate, ethylene- (propylene-diene monomer) copolymer (EPDM), and mixtures thereof And copolymers. For PVDF binders, the polymer may have a molecular weight of at least about 800,000 AMU. The use of high molecular weight PVDF polymers has been found to provide higher powder loadings on the positive electrode without adversely changing battery performance while obtaining physically stable electrodes. In some commercial embodiments, the battery generally includes a plurality of electrodes separated by the separator (s) such that the structure is stacked or rolled into the casing. The casing of the battery can be a polymer film, a metal foil, a metal can or a combination thereof. Thus, the battery formed may be a coin or button cell battery, a cylindrical battery, a prismatic battery or a pouch cell battery.

The resulting battery typically has a discharge energy density of about 240 Wh / kg or more when discharged from 4.6 V to 2.0 V. In some embodiments, the resulting battery may have a discharge energy density of at least about 250 Wh / kg to 550 Wh / kg. In further embodiments, the battery may have a volumetric discharge energy density of at least about 550 Wh / l. In some embodiments, the resulting battery may have a volumetric discharge energy density of at least about 650 Wh / l to 1150 Wh / l.

Batteries described herein are lithium ion batteries that generally employ a non-aqueous electrolyte comprising lithium ions. In the case of secondary lithium ion batteries, lithium ions are released from the cathode during discharge, such that the cathode acts as an anode during discharge while generating electrons from oxidation of lithium upon release of lithium ions from the electrode. Correspondingly, the anode absorbs lithium ions through intercalation or the like during discharge so that the anode acts as a cathode that consumes electrons to neutralize the lithium ions. Upon recharging of the secondary battery, the flow of lithium ions is reversed through a battery having a negative electrode that absorbs lithium and a positive electrode that releases lithium as lithium ions.

Some of the positive electrode material compositions described herein have a low fire risk for improved safety properties due to the layered structure and certain compositions with reduced amounts of nickel as compared to some other high capacity cathode materials. In addition, such compositions can be produced from starting materials that use small amounts of undesirable elements from an environmental standpoint and have a cost that is suitable for commercial scale production.

The term “element” is used herein in a conventional manner as mentioned in many periodic tables, and the element has an appropriate oxidation state when the element is present in the composition, and only when the element is mentioned as being in elemental form It exists in its elemental form M ⁰ . Thus, metal elements generally exist only in the metal state of the corresponding alloy in the elemental form of the metal or in the elemental form of the metal. In other words, metal oxides or other metal compositions other than metal alloys are generally not metallic.

Rechargeable batteries are, for example, mobile communication devices such as telephones, mobile entertainment devices such as MP3 players and televisions, portable computers, combinations of such devices that can be seen as universal, as well as transport devices such as cars and forklifts. Has a range of uses. Batteries described herein incorporating an improved cathode active material with respect to specific capacity and cycling can provide improved performance for consumers, particularly for medium current applications.

amount Electric activity  matter

The improved high energy batteries described herein generally incorporate both electroactive materials having a higher energy density compared to conventional materials. Such materials can be made to have suitable material properties such as tap density so that the powder can be effectively collected in batteries with corresponding high energy. Accordingly, suitably improved both electroactive materials have been found to be useful for making desirable batteries by the assembly process described herein.

If a corresponding battery with a positive electrode active material based on intercalation is in use, intercalation and release of lithium ions from the lattice will lead to changes in the crystalline lattice of the electroactive material. As long as these changes are inherently reversible, the capacity of the material does not change. However, it is observed that the dose of active substance is reduced due to cycling to varying degrees. Thus, after multiple cycles, if the battery performance falls below an acceptable value, the battery will be replaced. In addition, in the case of the first cycle of the cell there is generally an irreversible capacity loss that is significantly greater than the cycle capacity loss in subsequent cycles. The irreversible capacity loss is the difference between the charge capacity of the new cell and the first discharge capacity. To compensate for this irreversible capacity loss of the first cycle, extra electroactivity, so that the lost capacity is not easy for most of the life of the cell, so that the cell can be fully charged even though the negative material is basically consumed. The material is contained in the cathode.

Lithium ion batteries may use a lithium-rich positive electrode active material as compared to a standard, uniformly electroactive lithium metal oxide composition. Without wishing to be bound by theory, a suitably formed lithium-rich lithium metal oxide is, for example, a complex crystal structure in which Li ₂ MnO ₃ is structurally integrated with a layered LiMnO ₂ component or a spinel LiMn ₂ O ₄ component. Or a manganese ion is thought to have a similar composite composition substituted with other transition metal ions having an equivalent oxidation state. In some embodiments, the positive electrode material may be represented by xLiMO _2. (1-x) Li ₂ M'O ₃ in two component notation, wherein M is one or more trivalent metal ions and one or more metal ions is Mn ⁺³ , Co ^{+ 3} or Ni ^{+ 3} , M 'is one or more tetravalent metal ions, where 0 <x <1. Such compositions are described in US Pat. No. 6,677,082 ('082 Patent) by Thackeray et al. Entitled “Lithium Metal Oxide Electrodes for Lithium Cells and Batteries” and “Lithium Cells and Further described in US Pat. No. 6,680,143 ('143 patent) by Thackeray et al., Entitled &quot; Lithium Metal Oxide Electrodes for Lithium Cells and Batteries, " Cited for reference. Thackery specifically identified Mn, Ti and Zr in the case of M 'and Mn and Ni in the case of M.

Batteries formed from such materials have been observed to cycle at higher voltages and at higher capacities than batteries formed from corresponding LiMO ₂ compositions. In another embodiment, the layered lithium rich composition may be represented by xLi ₂ MnO _3. (1-X) LiMn _{2 - y} M _y O ₄ in two component notation, wherein M is one or more metal cations. Such compositions are further described in published US patent application 2006/0051673 by Johnson et al., Entitled “Manganese Oxide Composite Electrodes for Lithium Batteries”, which is incorporated herein by reference. Is cited. The positive electrode material having the composite crystal structure can have good cycling characteristics and exhibit high specific capacity of 200 milliampere hours / gram (mAh / g) or more at room temperature.

Some specific layered structures are described in Thackery et al., "Comments on the structural complexity of Lithium-rich Li _{1 + x} M _{1 - x} O ₂ electrodes (M = Mn, Ni, Co) for lithium batteries", Electrochemistry Communications 8 (2006), 1531-1538, which is incorporated herein by reference. The research reported in this literature is a composition having the formula _{Li 1 + x [Mn 0.5 Ni} 0.5] 1-x O 2 and _{Li 1 + x [Mn 0 .333} Ni 0 .333 Co 0 .333] 1- x O 2 Was reviewed. This document also describes the structural complexity of the layered material.

The inventors have also found that metal and fluorine dopants can affect the capacity, impedance and stability of the layered lithium metal oxide structure. Such compositions with suitable metals and fluorine dopants can similarly be used in the batteries described herein. Some embodiments of such metal and halogen element doping, such as fluorine doping compositions, are described in US patents by Kang et al., Entitled " Layered Cathode Materials for Lithium Ion Rechargeable Batteries. &Quot; Further described in US Pat. No. 7,205,072, which is incorporated herein by reference. Alterations doped with such metals and / or halogen elements on the layered lithium metal oxide structure can be similarly used in the high energy batteries described herein. We have found that metal fluoride compositions can be successfully used to stabilize cycling of high energy capacity compositions to maintain a discharge capacity of at least about 220 mAh / g for at least 10 discharge / recharge cycles.

The positive electrode active material with any fluorine dopant may be described by the formula Li _{1 + x} Ni _α Mn _β Co _γ M _δ O _{2 -z / 2} F _z , where x ranges from about 0.05 to about 0.25, α is in the range of about 0.1 to about 0.4, β is in the range of about 0.4 to about 0.65, γ is in the range of about 0.05 to about 0.3, δ is in the range of about 0 to about 0.1, and z is about 0 to about In the range of 0.1, M is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb or a combination thereof. Fluorine is a dopant that can contribute to the cycling stability as well as the improved safety of the material. In some embodiments where z = 0, this formula is reduced to Li _{1 + x} Ni _α Mn _β Co _γ M _δ O ₂ . We have found that although having fluorine dopants may be desirable in some embodiments, a suitable coating provides a desirable improvement in cycling properties without the use of fluorine dopants. Moreover, in some embodiments, it is desirable for the composition to have δ = 0 so as to be more simplified while still providing improved performance. For such embodiments, if z = 0 as well, the formula is simplified to Li _{1 + x} Ni _α Mn _β Co _γ 0 ₂ , with the parameters as outlined above. The composition represented by the formula Li _{1 + x} Ni _α Mn _β Co _γ 0 ₂ may alternatively be described in the two component notation mentioned above. Those skilled in the art will recognize that further ranges of parameter values are contemplated and fall within the context of the present invention within the above apparent range.

High specific capacity is defined as "Positive Electrode Material for Lithium Ion Batteries Having a High Specific Discharge Capacity and Processes for the Synthesis of these Materials". U.S. Application No. 12 / 246,814 (the '814 application) by Venkatachalam et al. And "Positive Electrode Material for High Specific Discharge Capacity Lithium Ion Batteries" United States Application Serial No. 12/332 735 No. of these _{Li 1 + x Ni α Mn β} Co γ M δ 0 2-z / 2 F z compositions using the synthesis method described in the ( '735 application) by such Lopez to that Both of which are incorporated herein by reference. In particular, surprisingly good results have been obtained for _{Li [Li 0 .2 Ni 0 .175} Co 0 .10 Mn 0 .525] 0 2. The carbonate coprecipitation process described in the '735 application forms a preferred lithium rich metal oxide material having cobalt in the composition and presenting high specific capacity performance with excellent tap density. This co-pending patent application also describes the use of coatings effective to improve performance and cycling.

Suitable coating materials may not only improve the long term cycling performance of the material but also reduce the irreversible capacity loss of the first cycle. Without wishing to be bound by theory, this coating can stabilize the crystal lattice during absorption and release of lithium ions such that the irreversible change in the crystal lattice is significantly reduced. In particular, metal fluoride compositions can be used as effective coatings. The general use of metal fluoride compositions as coatings for cathode active materials, in particular LiCoO ₂ and LiMn ₂ O ₄ , has been described as "Cathode Active Material Coated with Fluorine Compound. for Lithium Secondary Batteries and Method for Preparing the Same) is disclosed in published PCT application WO 2006/109930 A ('930 application) by Sun et al., which is incorporated herein by reference. This patent application provides results for LiCoO ₂ coated with LiF, ZnF ₂ or AlF ₃ . We have found that metal fluoride coatings can provide a significant improvement over the lithium rich layered positive electrode active material described herein. Such improvements are associated with long term cycling due to significantly reduced capacity degradation, significant reduction in irreversible capacity loss of the first cycle, and improvement in general capacity. The amount of coating material can be chosen such that the improvement in observed performance is enhanced.

In particular, the inventors have found that the cycling properties of batteries formed from lithium metal oxides coated with metal fluoride are significantly improved from uncoated materials. In addition, the overall capacity of the battery also exhibits desirable properties by the fluoride coating and the irreversible capacity loss of the first cycle of the battery is reduced. As discussed above, the irreversible capacity loss of the first cycle of the battery refers to the difference between the charging capacity of the new battery and its first discharge capacity. The bulk of the irreversible capacity loss of the first cycle is generally due to the positive electrode material.

The coating provides an unexpected improvement in the performance of the high capacity lithium rich composition used herein. In general, selected metal fluorides or nonmetal fluorides may be used for the coating. Similarly, coatings with combinations of metal and / or nonmetallic elements can be used. Metal / nonmetal fluoride coatings have been proposed to stabilize the performance of positive electrode active materials for lithium secondary batteries. Suitable metal and nonmetallic elements for fluoride coatings include, for example, Al, Bi, Ga, Ge, In, Mg, Pb, Si, Sn, Ti, Tl, Zn, Zr and combinations thereof. Aluminum fluoride may be a preferred coating material because it is considered environmentally good at a reasonable cost. Metal fluoride coatings are described generally in the '930 application by Sun et al. Of Sun PCT application, which is referred to as the concrete has fluoride composition to be described later, CsF, KF, LiF, NaF , RbF, TiF, AgF, AgF 2, BaF 2, CaF 2, CuF 2, CdF 2, FeF 2, HgF 2 , Hg ₂ F ₂ , MnF ₂ , MgF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF _{3 , GaF 3, GdF 3, FeF} 3, HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, VOF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF _{3, YF 3, YbF 3,} TlF 3, CeF 4, GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF ₆ , SF ₆ , and WF ₆ are shown.

LiNi _1/3 Co _1/3 the effect of AlF ₃ coating on the cycling performance of the Mn _1/3 O ₂ may be found in _{[Sun et al, "AlF 3} -Coating to Improve High Voltage Cycling Performance of Li [Ni 1/3 Co _{1/3 Mn 1/3]} O and is described in a _{2 Cathode Materials for Lithium Secondary Batteries,} "J. of the Electrochemical Society, 154 (3), adding from A168-A172 (2007)]. _{Also, LiNi 0 .8 Co 0 .1 Mn} 0 .1 effect of AlF ₃ coating on the cycling performance of the O ₂ is described in [Woo et al., "Significant Improvement of Electrochemical Performance of AlF 3 -Coated Li [Ni 0.8 Co _0.1 Mn _0.1 ] 0 ₂ Cathode Materials, "J. of the Electrochemical Society, 154 (11) A1005-A 1009 (2007), which is incorporated herein by reference. Reduction of irreversible capacity loss by Al ₂ O ₃ coatings is described by Wu et al., “High Capacity, Surface-Modified Layered Li [Li _{(1-x) / 3} Mn _{(2-x) / 3} Ni _{x / 3} Co _{x / 3} ] O ₂ Cathodes with Low Irreversible Capacity Loss, "Electrochemical and Solid State Letters, 9 (5) A221-A224 (2006), which is incorporated herein by reference.

The inventors have found that the metal / non-metal fluoride coating has a positive electrode material for lithium ion batteries having a high discharge specific capacity and a method for synthesizing the material. US Patent No. 12 / 246,814 (the '814 application) and "Positive Electrode Mateiral for High Specific Discharge Capacity Lithium Ion Batteries" by Venkatachalam et al. Performance of Lithium Rich Layered Compositions for Lithium Ion Secondary Batteries as Proven by Example in US Pat. No. 12 / 332,735 ('735 Application) (referenced herein) by Lopez et al. It was found that can be significantly improved. This coating improves the capacity of the battery. However, the coating itself is not electrochemically active. If the loss of specific amount is exceeded due to the amount of coating added to the sample, the benefits of the coating addition are offset by its electrochemical inertness, and a reduction in battery capacity can be expected. In general, an amount of coating may be selected to balance the beneficial stabilization resulting from the coating with the loss of specific capacity due to the weight of the coating material, which generally does not directly contribute to the high specific content of the material. Generally, the amount of coating material ranges from about 0.01 mol% to about 10 mol%, in further embodiments ranges from about 0.1 mol% to about 7 mol%, and in further embodiments, from about 0.2 mol% to about 5 mol%. And in another embodiment in a range from about 0.5 mol% to about 4 mol%. Those skilled in the art will recognize that further ranges of coating materials are contemplated and fall within the specification of the present invention within the above apparent scope. The amount of AlF ₃ effective to enhance the capacity of the uncoated material in the AlF ₃ coated metal oxide material is related to the particle size and surface area of the uncoated material. In particular, higher mole percent metal fluoride coatings may generally use higher surface area powders to realize an effect equivalent to coatings for lower surface area powders.

The positive electrode active composition can exhibit surprisingly high specific capacities in lithium ion cells under substantial discharge conditions. In some embodiments based on improved synthetic methods, the lithium rich positive electrode active material with a composite crystal structure may have good cycling properties for discharging at 4.6 V and exhibit high specific capacity of at least 250 mAh / g at room temperature. In some other embodiments, the lithium rich positive electrode active material having a composite crystal structure as used herein has a high cycling density and a high tap density of at least 1.8 g / ml for discharge at 4.6 V and is at least 235 mAh / g at room temperature. It can represent specific quantities. In general, when the specific amounts are comparable, the higher tap density of the positive electrode material leads to the higher overall capacity of the battery. Note that during charge / discharge measurements, the specific capacity of the material depends on the rate of discharge. The maximum capacity of a particular cell is measured at very slow discharge rates. In actual use, the actual capacity has a capacity less than the maximum due to the discharge at a limited rate. More substantial capacity can be measured using a suitable discharge rate, more similar to the rate during use. For low to medium speed applications, a suitable test rate involves more than 3 hours of battery discharge. In conventional notation, this is described as C / 3 or 0.33C. As used herein, the positive electrode active material may have a discharge specific capacity of at least about 250 mAh / g at a discharge rate of C / 3 in a tenth discharge / charge cycle at room temperature when discharged at 4.6 V. In some embodiments, the positive electrode active material used herein may have a discharge specific capacity of at least about 250 mAh / g at a discharge rate of C / 10 at room temperature when discharged at 4.6 V and the tap density is at least 1.8 g / ml. The coated material yielded the best capacity performance in lithium ion batteries.

Anode materials generally invent "Positive Electrode Material for Lithium Ion Batteries Having a High Specific Discharge Capacity and Processes for the Synthesis of these Materials" US Patent No. 12 / 246,814 (the '814 application) by Venkatachalam et al. And " Positive Electrode Material for High Specific Discharge Capacity Lithium Ion Batteries " Synthesized by co-precipitation and sol-gel processes described in detail in U.S. Application No. 12 / 332,735 ('735 Application) (incorporated herein by reference) by Lopez et al. Silver is synthesized by precipitating a mixed metal hydroxide or carbonate composition from a solution comprising a +2 cation, wherein the hydroxide or carbonate Composition has a selected composition, the metal hydroxide or carbonate precipitate is then subjected to thermal treatment to form a crystalline layered lithium metal oxide composition.

The elemental lithium may be incorporated into the material in one or more selected steps of the process. For example, lithium salts can be incorporated into the solution prior to the precipitation step or during the precipitation step by adding a hydrated lithium salt. In such a method, lithium species are incorporated into the carbonate material in the same manner as other metals. In addition, due to the nature of lithium, elemental lithium can be incorporated into materials in solid phase reactions without adversely affecting the resulting characteristics of the product composition. Thus, for example, generally a suitable amount of lithium source as a powder, such as LiOH.H ₂ O, LiOH, Li ₂ CO ₃ , or a combination thereof, can be mixed with the precipitated metal hydroxide or carbonate. The powder mixture is then subjected to a heating step (s) to form an oxide followed by a crystalline anode material.

The fluoride coating of the positive electrode material can be deposited using a solution based precipitation method. The powder of the positive electrode material can be mixed in a suitable solvent such as an aqueous solvent. Preferred soluble compositions of metal / nonmetals can be dissolved in a solvent. NH ₄ F may then be gradually added to the dispersion / solution to precipitate the metal fluoride. The total amount of coating reactants may be selected to form the desired amount of coating, and the ratio of coating reactants may be based on the stoichiometry of the coating material. The coating mixture may facilitate the coating process by heating the aqueous solution during the coating process for about 20 minutes to about 48 hours at a suitable temperature, such as in the range of about 60 ° C to about 100 ° C. After removing the coated electroactive material from the solution, the material may be dried and heated to a temperature of about 250 ° C. to about 600 ° C. for about 20 minutes to about 48 hours to complete the formation of the coated material. The heating can be carried out under a nitrogen atmosphere or under an oxygen free atmosphere.

Battery cell structure

In the battery improved herein, the high energy positive electrode material described above is efficiently incorporated into the battery to achieve a high performance value. In particular, the ability to synthesize high energy density electroactive materials with high tap density has been found to allow the anode to load high active materials. The inventors have also found that high molecular weight polymers form electrodes with small amounts of polymer without degrading the physical stability of the electrode or electrode performance. Based on this significant improvement, the battery can be formed to have a high volume energy as well as a very high energy density. 1 shows a schematic of a battery without a casing. Specifically, battery 100 is schematically illustrated as having a cathode 102, an anode 104, and a separator 106 between cathode 102 and anode 104. The battery may include, for example, a separator suitably arranged with a plurality of positive electrodes and a plurality of negative electrodes in a stack. The electrolyte in contact with the electrode provides ionic conductivity through the separator between the electrodes of opposite polarity. Batteries generally include current collectors 108 and 110 associated with negative electrode 102 and positive electrode 104, respectively. Alternatively, the electrodes and separators can be gel-rolled or folded in different batches before enclosing in the casing.

Commercial cells are generally designed to have excess capacity at the negative electrode as compared to the positive electrode such that the cell is not limited by the anode during discharge and that lithium metal is not plated out on the negative electrode during battery recharge. Lithium metal cans present not only cycling problems but also safety problems due to the reactivity of lithium metals. In order to realize the high energy desired for the cell, the negative electrode structure can be made thicker so that the negative electrode can provide an appropriate capacity in view of very high positive electrode capacity.

The high energy battery described herein may have a negative electrode formed, for example, with a conventional lithium intercalated carbon material. Suitable negative electrode active materials include, for example, lithium intercalated carbon, some metal alloys, some silicon materials, and some metal oxides. The separator is disposed between the positive electrode and the negative electrode. The electrode stack is in contact with an electrolyte comprising lithium ions and generally a non-aqueous liquid. The electrode stack and electrolyte are sealed in a suitable container.

The nature of the negative intercalation material affects the resulting battery voltage because the voltage is the difference voltage between the half cell potentials at the cathode and anode. Suitable negative electrode lithium intercalating compositions are, for example, graphite, synthetic graphite, hard carbon, mesophase carbon, suitable carbon black, coke, fullerene, niobium pentoxide, intermetallic alloys, silicon alloys, tin alloys, silicon, titanium oxide, tin oxide And lithium titanium oxide, such as Li _x TiO ₂ , 0.5 <x ≦ ₁ or Li _{1 + x} Ti _2-x 0 ₄ , 0 ≦ _x ≦ 1/3. Hard carbon suitable for use in the negative electrode is US patent application 2003 / 0157014A to Wang et al. Entitled "Pyrolyzed Hard Carbon Material, Preparation and its Applications". It is further described in, which is incorporated herein by reference. Alloy based anodes are described, for example, in US Pat. No. 6,730,429 to Thackeray et al., Entitled "Intermetallic Nagative Electrodes for Non-Aqueous Lithium Cells and Batteries." Published US patent application Ser. No. 2007/0148544 A1 by Le, entitled " Silicon-Containing Alloys Useful as Electrodes for Lithium-Ion Batteries, " Further described in US Pat. No. 7,229,717 to Yamaguchi et al. Entitled "Anode Active Material and Battery Using it", all three of which are incorporated herein by reference. The metal alloy may be combined with intercalated carbon and / or conductive carbon. The negative electrode active material can be combined with the polymeric binder and associated with the current collector to form the negative electrode. Similarly, other suitable electroactive cathode compositions may be used which provide a suitable discharge voltage with the desired cycling function. Additional negative electrode material is co-pending patent pending by Kumar entitled "Inter-metallic Compositions, Nagative Electrodes With Inter-Metallic Compositions and Batteries". Serial number 61 / 002,619 and serial number 61 / 125,476 by Kumar et al., Entitled "Lithium Ion Batteries With Particular Negative Electrode Compositions", Both of these documents are incorporated herein by reference. In some embodiments, the negative electrode may have a thickness of 65 microns to 200 microns, and in further embodiments 75 microns to 150 microns on each side of the current collector after compacting the anode material. In some embodiments, the anode has a density of about 1.5-1.7 g / ml. Those skilled in the art will recognize that further ranges of electrode thicknesses are contemplated within the above apparent range and are within the scope of the present disclosure.

The positive electrode active composition and the negative electrode active composition are generally powder compositions that are held together at the corresponding electrode with a polymeric binder. The binder provides ionic conductivity to the active particles when in contact with the electrolyte. Suitable polymer binders are, for example, polyvinylidene fluoride (PVDF), polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylates, rubbers, such as ethylene-propylene-diene monomer (EPDM) rubber or styrene Butadiene rubber (SBR), copolymers thereof and mixtures thereof. The loading of the positive electrode active material in the binder can be high, for example greater than about 80% by weight. Large loadings of the powder of the positive electrode active material in such a positive electrode can be formed with more preferred and reproducible physical stability using polymers with high molecular weight. In particular, in some embodiments, the PVDF polymer binder has an average of at least about 800,000 atomic weight units (AMUs), at least about 850,000 AMU in further embodiments, at least about 900,000 AMU in further embodiments, and about 1,000,000 AMU to 5,000,000 AMU in further embodiments. Have a molecular weight. Those skilled in the art will recognize that further ranges of the compositions are considered within the above apparent scope and are within the scope of the present disclosure. To form the electrode, the powder can be combined with the polymer in a suitable liquid, such as a solvent for the polymer. The resulting paste may be pressed into the electrode structure.

The positive electrode composition, and possibly the negative electrode composition, also generally comprises an electrically conductive powder, separate from the electroactive composition. Suitable supplemental electrically conductive powders include, for example, graphite, carbon black, metal powders such as silver powder, metal fibers such as stainless steel fibers, and the like, and combinations thereof.

The electrode is generally associated with an electrically conductive current collector to facilitate the flow of electrons between the electrode and the external circuit. The current collector may comprise a metal, such as a metal foil, a metal grid or screen, or a whole body metal. Full-body metal current collector refers to a metal grid having a thicker thickness that allows a greater amount of electrode material to be disposed within the metal grid. In some embodiments, the current collector may be formed from nickel, aluminum, stainless steel, copper, and the like. The electrode material may be cast in contact with the current collector. For example, in some embodiments, the electrode material in contact with the current collector foil or other structure may be subjected to a pressure of about 2 to about 10 kg / cm ² (kg / square centimeter). The compacted structure can be dried, for example, in an oven to remove solvent from the electrode. The metal foil can be used as the current collector. For example, copper foil can be used as the current collector for negative electrode and aluminum foil can be used as the current collector for positive electrode. Pastes or slurries of the cathode material may be coated on both sides of the foil. The electrode may then be pressed using a calendering roll, a die with a die, or other suitable processing device to compress the electrode to the desired thickness. The positive electrode may have 20 mg / cm ^{2 to} 50 mg / cm ² of active material particles loaded on each side of the current collector. The positive electrode may have a density of at least 2.5 grams / milliliter (g / ml), in further embodiments at least about 2.8 g / ml, and in further embodiments at least about 3.0 g / ml to about 3.5 g / ml. Those skilled in the art will appreciate that further ranges of active substance loadings are considered within the above apparent scope and are within the scope of the present disclosure.

The separator is positioned between the anode and the cathode. The separator is one that is electrically insulated while providing at least selected ion conductivity between the two electrodes. Various materials can be used as the separator. For example, glass fibers formed in a porous mat can be used as the separator. Commercial separator materials are generally formed from polymers, such as polyethylene and / or polypropylene, which are porous sheets that provide ionic conduction. Commercial polymer separators include, for example, the Celgard ^® line of separator materials from Hoechst Celanese (Charlotte, NC, USA). Suitable separator materials are, for example, a 12 micron to 40 micron thick 3-layer polypropylene and a polypropylene sheet, for example, Celgard ^® M824 having a thickness of 12 micron polyethylene. In addition, ceramic-polymer composite materials have been developed for separator applications. Such composite separators can be stable at high temperatures, and the composite material can significantly reduce the risk of fire. Polymer-ceramic composites for separator materials are described in US Patent Application No. 2005/0031942 by Hennige et al. Entitled “Electric Separator, Method for Producing the Same and the Use Thereof”. It is further described in A, which is incorporated herein by reference. Polymer-ceramic composites for lithium ion battery separators are commercially available from Evonik Industries under the trade name Separion®.

The electrolyte for a lithium ion battery may comprise one or more of those selected from lithium salts. Suitable lithium salts generally have inert anions. Suitable lithium salts are, for example, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoromethyl sulfonyl imide), lithium trifluoromethane sulfonate, lithium tris (trifluoromethyl Sulfonyl) metades, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride and combinations thereof. Typically, the electrolyte comprises a lithium salt at a concentration of 1 M. In some embodiments, a conventional electrolyte composition, such as a 1 molar solution of LiPF ₆ , may be used in the combination of ethylene carbonate and dimethylcarbonate to 1 to 1 L by volume ratio. In some specific embodiments, solid electrolytes may also be used that generally also serve as separators for the electrodes. Solid electrolytes are, for example, added to US Pat. No. 7,273,682 to Park et al. Entitled "Solid Electrolyte, Method for Preparing the Same, and Battery Using the Same". Which is incorporated herein by reference.

For lithium ion batteries of interest, non-aqueous liquids are generally used to dissolve the lithium salt (s). The solvent is generally inert and does not dissolve the electroactive material. Suitable solvents are, for example, propylene carbonate, dimethyl carbonate, diethyl carbonate, 2-methyl tetrahydrofuran, dioxolane, tetrahydrofuran, methyl ethyl carbonate, γ-butyrolactone, dimethyl Sulfoxide, acetonitrile, formamide, dimethyl formamide, triglyme (tri (ethylene glycol) dimethyl ether), diglyme (diethylene glycol dimethyl ether), DME (glyme or 1,2-dimethyloxyethane or ethylene Glycol dimethyl ether), nitromethane and mixtures thereof.

The electrodes described herein can be incorporated into various commercial cell structures. For example, the cathode composition can be used in prismatic cells, wound cylindrical cells, coin cells, pouch cells or other suitable cell shapes. In the examples the tests are performed using coin-type and pouch-type cells. The cell may comprise a single anode structure, or a stacked structure having a plurality of anodes assembled in parallel and / or series electrical connection (s). In particular, the battery may alternately comprise a stack of positive and negative electrodes and a separator therebetween. Generally, a plurality of electrodes are connected in parallel to increase the current at a voltage achieved with a pair of anodes and cathodes. While positive electrode active materials are used in batteries for primary or single charge use, the resulting batteries generally have cycling characteristics desirable for secondary battery use over multiple cycling of cells.

In some embodiments, the positive electrode and the negative electrode can be laminated with a separator therebetween, and the resulting laminated structure can be rolled into a cylindrical or prismatic arrangement to form a battery structure. Suitable electrically conductive tabs may be welded to the current collector and the like, and the resulting gel-rolling structure may be placed in a metal canister or polymer package and the negative and positive tabs are welded with appropriate external contacts. The electrolyte is added to the canister and seals the canister or package to complete the battery.

Some previously used rechargeable commercial cells include, for example, cylindrical 18650 cells (18 mm in diameter, 65 mm in length) and 26700 cells (26 mm in diameter, 70 mm in length), although other cell sizes may also be used. Cylindrical cells are a widely used battery packaging format. Cylindrical cells have the ability to withstand high internal and external pressures. In addition, the cylindrical cell may have a venting mechanism that releases excessive internal pressure. However, because of the cylindrical shape and fixed size of these cells, cylindrical battery cells generally have low space utilization and must be designed to the size of available cells. In cylindrical cells, the electrodes and separators can be made into long thin sheets and optionally rolled in needle or gel-rolling around both rod-shaped terminals. Alternatively, the electrode can be wound on a flat mandrel to provide a flat shape which can be mounted inside a prism case to produce a prismatic cell. The electrodes may alternatively or additionally be stacked in a prismatic cell.

Prismatic cells can be manufactured in various sizes to be tailored to meet various sizes and energy consumptions. One version of a prismatic cell is referred to as a pouch cell, which generally has a heat shield foil that surrounds the rolled or stacked electrodes and separators as an alternative to metal cans. Pouch-type battery battery formats are generally adjusted to the correct cell dimensions and allow the available space to be used most efficiently and sometimes achieve the highest packaging efficiency of 90-95% of battery packs. Due to the absence of metal cans, pouch-type batteries are generally light. Prismatic and pouch cell formats can contain a plurality of positive electrode sheets and negative electrode sheets inserted together in a layer with a separator between the positive and negative electrodes.

In order to realize very high energy for the cells described herein, the positive electrode structure generally comprises the high capacity cathode electroactive composition described herein. However, anodes also generally involve high loadings of electroactive material and corresponding reductions in electrically conductive powders and binders into the electrodes. The electrode should have adequate cohesion at high particle loadings. This can be achieved by appropriate choice of polymer binders, for example by using high molecular weight binders and / or rubber polymers.

In some specific embodiments, the positive electrode is about 90 to about 99 weight percent, about 92 to 98 weight percent in further embodiments, about 92. to about 97.5 weight percent in further embodiments, about 92.5 to about 97 weight in other embodiments May comprise% active material. Similarly, the positive electrode may comprise from about 0.1 to about 8 weight percent, in further embodiments from about 0.5 to about 6 weight percent, and in further embodiments from about 1 to about 5 weight percent supplementary electrically conductive material. In addition, the positive electrode may comprise from about 0.5 to about 8 weight percent of a polymeric binder, in further embodiments from about 1.0 to about 6 weight percent of a polymeric binder, and in further embodiments from about 1.5 to about 5 weight percent of a polymeric binder. Those skilled in the art will appreciate that further ranges of positive electrode composition amounts are contemplated and fall within the context of the present invention within the above apparent range. Suitable conductive materials include, for example, graphite powder, carbon black, combinations thereof, and the like.

The batteries described herein are formed from active materials that provide a high degree of safety. Commercial lithium-ion batteries suffer from safety issues due to the case of fired batteries. In contrast to commercial cells with relatively high energy capacities, the cells of the present invention do not exhibit thermal run away because the cells described herein are based on materials that do not have corresponding instability. When the cell described herein is heated, the cell does not react naturally to ignite. A relatively high energy commercial lithium ion battery exhibits thermal runaway, and the heated battery undergoes a reaction and catches fire. Thus, the cells of the present invention not only provide improved energy capacity but also provide increased safety during use.

Improved battery performance

As mentioned above, the positive electrode active material has a high energy capacity, generally at least about 200 milliamp hours / gram (mAh / g), in some embodiments at least about 225 mAh / g, with good cycling, in further embodiments May have about 250 mAh / g or more. By virtue of the cell structure described herein, the battery is about 240 watt-hours / kg (Wh / kg) in a battery of the desired shape and size, about 250-550 Wh / kg in further embodiments, about 280 in some embodiments It may have a total energy density of ˜500 Wh / kg, in further embodiments about 300-450 Wh / kg. Alternatively, when measured in terms of volume, the battery is at least about 550 watt-hours / liter (Wh / l) in a battery of the desired shape and size, in further embodiments from about 650 to 1150 Wh / l, in some embodiments At about 675-1050 Wh / l, and in further embodiments, at about 700-1000 Wh / l. The volume of the battery can be obtained, for example, by multiplying the cross section area of the cell canister by the length of the cell canister, or by multiplying the length of the battery cell by the width and thickness. Those skilled in the art will appreciate that further ranges of battery capacity are contemplated and fall within the specification of the present invention within the apparent scope above.

In contrast to the cell structure of the present invention, US Pat. Nos. 7,201,997 and 7,166,385 (both of which are incorporated herein by reference), both by Ishida et al., Are energy density versus electrode thickness in terms of lithium ion batteries with high energy density active materials. Details are included, including lifetime, rate and rate capability. Both anode and cathode thicknesses vary from 60 to 360 microns and the data indicate that life and charge and discharge efficiency significantly decrease with increasing electrode thickness. This cell structure incorporates a conventional positive electrode active material. The patent documents do not report the level of performance realized in the context. In the cells described herein, the positive electrode can be thinner, not only providing high energy through higher capacity active materials, but also using more loaded active materials.

In general, various similar test procedures can be used to evaluate battery performance. Described herein are specific test procedures for evaluating the described performance values. The test procedure is described in more detail in the Examples below. Specifically, the battery can be cycled between 4.6 V and 2.0 V at room temperature, although other ranges with correspondingly different results may be used. Evaluation of the range from 4.6 V to 2.0 V is desirable for commercial use because batteries generally have stable cycling in this voltage range. For the first third cycle, the battery is discharged at a rate of C / 10 to achieve irreversible capacity loss. The battery then cycles a third cycle at C / 5. In the case of the seventh and subsequent cycles, the battery is cycled at a rate of C / 3, which is a test rate suitable for medium current applications. Likewise, the notation C / x means that the battery is discharged at a lower voltage cutoff selected at x time at a rate of completely discharging the battery. Battery capacity generally varies significantly with discharge rate as capacity is lost as discharge rate increases.

In some embodiments, the positive electrode active material is at least 235 milliamp hours / gram (mAh / g), in further embodiments from about 240 mAh / g to about 310 mAh / g, in further embodiments from about 245 mAh / g to about 300 mAh / g, in other embodiments from about 250 mAh / g to about 290 mAh / g, having a specific capacity for a tenth cycle at a C / 3 discharge rate. Additionally, the 20th cycle discharge capacity of the material is at least about 98% of the fifth cycle discharge capacity cycled at a discharge rate of C / 3, and in further embodiments 98.5%. The inventors have found that the first cycle irreversible capacity loss for the metal fluoride coated electroactive material can be reduced by at least about 25% compared to the equivalent performance of the uncoated material, and in further embodiments from about 30% to about 60%. Found out. The tap density of the material may be at least about 1.8 g / ml, in further embodiments from about 2 to about 3.5 g / ml, and in further embodiments, from about 2.05 to about 2.75 g / ml. The high tap density translates into the overall high capacity of the battery provided in fixed volumes. Those skilled in the art will appreciate that further ranges of reduction in specific capacity and tap density, and irreversible capacity loss within the above apparent range are considered and are within the context of the present disclosure. For fixed volume applications, such as batteries for electronic devices, high tap density and thus overall high capacity of the battery is of particular importance.

In general, the tap density is the apparent powder density obtained under the mentioned tapping conditions. The apparent density of the powder depends on how tightly the individual particles of the powder are packed together. Apparent density is influenced by the true density of the solids as well as by the particle size distribution, particle shape and cohesiveness. Handling or vibration of the powdered material allows some cohesion to be overcome, which allows the particles to move together so that smaller particles can move forward as they act as spaces between the larger particles. As a result, the total volume occupied by the powder is reduced and the density of the powder is increased. Ultimately, additional natural particle packing could not be measured without the addition of pressure and realized the upper limit of particle packing. Pressured electrodes are formed, but moderate amounts of pressure are only effective at forming a particular packing density of electroactive material at the battery electrode. Since the actual density at the electrode is generally related to the tap density measured at the powder, the tap density measurement makes the packing density expected at the battery electrode with the higher tap density corresponding to the higher packing density at the battery electrode.

In Examples 1-3, batteries with different packaging (eg, coin-to-pouch cells) were constructed and tested. The resulting battery was tested with a Maccor cycle tester to obtain cycling stability over charge-discharge curves and number of cycles.

Example  One - Coin type  Determined from cell battery measurements Cathode  Volume

This example demonstrates the high energy density available from a battery having a positive electrode formed with a high loading of active material. The active material has a high energy capacity as well as particle properties which provide a high loading in the electrode.

The positive electrode was formed by a cathode powder having a surface coating of aluminum fluoride O _2.0 and the formula _{Li [Li 0 .2 Ni 0 .175} Co 0 .01 Mn 0 .525]. This material was synthesized as described in the Examples of the '735 Application. The cathode powder was mixed with conductive carbon in a jar mill for several hours. The resulting powder was mixed with PVDF and N-methyl pyrrolidone (NMP) solution using a magnetic stirrer to form a homogeneous slurry. PVDF had an average molecular weight of 1 million atomic weight units (AMU). The slurry was coated on the aluminum foil to the desired thickness and then vacuum dried. The dried coating foil was compressed to the desired thickness and the electrodes were punched out of the coated foil to facilitate the coin cell battery. The electrode thus formed contained 94.25 wt% cathode powder, 3 wt% conductive carbon and 2.75 wt% PVDF binder. Electrode has a payload level of 18.1 mg / cm ² And an active cathode material of density 3.0 g / ml. In general, when equivalent electroactive powders and electrically conductive carbons are processed by PVDF polymers having a molecular weight significantly lower than 1 million AMU, the resulting structures will exhibit poor performance and assembly due to insufficient adhesion and cohesiveness of the electrode materials. I had a hard time.

The coin cell battery was assembled in an argon filled dry box using 1 M LiPF ₆ . Lithium foil was used as the negative electrode and a commercial separator material was placed between the positive and negative electrodes. This battery cell was cycled at room temperature at a C / 10 rate, ie, the rate at which the battery cell was discharged at 10 hours. The battery cells were tested for performance with a Maccor ^™ Battery Cell Tester. 1 shows the charge and discharge capacity of a first charge-discharge cycle of a coin cell battery. As shown in FIG. 1, the cathode material exhibited an initial charge capacity of 310 mAh / g and a discharge capacity of 277 mAh / g. Battery cells were cycled between 4.6 V and 2.0 V at various speeds. 2 shows the cycling stability of a battery cell measured up to 50 cycles. For the first third cycle, the battery was discharged at a rate of C / 10 to achieve irreversible capacity loss. The battery was then cycled on a third cycle at C / 5. For the seventh and subsequent cycles, the battery was cycled at a rate of C / 3, a test rate suitable for medium current applications. Likewise, the notation C / x means that the battery is discharged with the lower voltage cutoff selected at x time at the rate of completely discharging the battery.

Example  2 - Other Coin type  Determined from cell battery measurement Cathode  Volume

This example demonstrates the high energy capacity available for coin cell batteries with an anode comprising a lithium intercalation material. Coin-type cells had a positive electrode formed by a high loading of active cathode material.

The positive electrode was formed by using the cathode powder having a surface coating of aluminum fluoride O _2.0 and the formula _{Li [Li 0 .2 Ni 0 .175} Co 0 .01 Mn 0 .525]. Cathode powder was mixed with conductive carbon in a magnetic mill for several hours. The resulting powder was mixed with PVDF and N-methyl pyrrolidone (NMP) solution using a magnetic stirrer to form a homogeneous slurry. The PVDF used had an average molecular weight of 1 million AMU. The slurry was coated on the aluminum foil to the desired thickness and then vacuum dried. The dried coating foil was compressed to the desired thickness and the electrodes were punched out of the coated foil to facilitate the coin cell battery. The electrode thus formed contained 94.25 wt% cathode powder, 3 wt% conductive carbon and 2.75 wt% PVDF binder. The electrode has an active cathode material of loading level 20.2 mg / cm ² .

The coin cell battery was assembled in an argon filled dry box using 1 M LiPF ₆ . Graphite carbon coated on copper foil is used as the cathode and a triple layer (polypropylene / polyethylene / polypropylene) micro-porous separator (2320 from Celgard, LLC, NC) is placed between the anode and the cathode It was. This battery cell was cycled at room temperature at C / 10 rate, ie, the rate at which the battery cell was discharged and charged in 10 hours. The battery cells were tested for performance with a Maccor ^™ Battery Cell Tester. 3 shows the charge-discharge capacity of a coin cell battery between 4.55 V charge and 2.5 V discharge cutoff. As shown in FIG. 3, the cathode material exhibited a discharge capacity of 260 mAh / g over the given cycle range, and the discharge rate varied in later cycles as described in Example 1.

Example  3-determined from pouch cell battery measurement Cathode  Volume

This example demonstrates the high energy capacity available for pouch-type battery batteries formed by high loadings of active cathode material. Pouch type with dimensions 190 mm x 95 mm x 8 mm (volume = 0.14 L) adapted for a pouch-type cell battery having a stack of separators separated by separators according to the same configuration and test approach as outlined in Example 2 The cell battery was constructed. The positive electrodes were connected in parallel, and the negative electrodes were similarly connected in parallel. 5A shows a front photograph of a pouch-type battery battery. 5B shows a side photograph of the pouch-type battery battery. 5C shows the discharge curve of a pouch-type cell battery having 23 Ah and an energy density of 250 Wh / kg.

The data shown in Examples 1 and 2 above demonstrate a cathode capacity of 277 mAh / g using a lithium anode at C / 10 cycling rate and a cathode capacity of 260 mAh / g using a carbon anode, respectively. The anodes discussed herein have been shown to support a 25 amp-hour actual battery structure and the data are shown in Tables 1 and 2 below. The volumetric energy density of the battery is in the range of 550-650 Wh / l at C / 10 cycling speed. As a comparison, performance results using commercial LiCoO ₂ have been shown to yield 425-525 Wh / l at C / 10 cycling rates when used using the same electrode porosity as the cathode of the examples.

The above embodiments are intended to be illustrative and not intended to be limiting. There is another embodiment within the claims. In addition, while the present invention has been described in connection with specific embodiments, those skilled in the art will recognize and appreciate that changes may be made in form and specification without departing from the spirit and scope of the invention. All reference citations of the foregoing documents are limited so that the subject matter contrary to the apparent disclosure of this specification is not cited.

Claims (35)

A lithium ion secondary battery comprising a positive electrode comprising a positive electrode active material and a binder, a negative electrode including a first lithium intercalation composition, an electrolyte including lithium ions, and a separator between the positive electrode and the negative electrode, the battery at 4.6 V. And a discharge energy density of at least about 240 Wh / kg when discharged at 2.0 V, and wherein the positive electrode active material comprises a second lithium intercalation composition. The method of claim 1, wherein the positive electrode comprises at least about 92% by weight of a positive electrode active material, and the second lithium intercalating composition is represented by the formula xLiMO ₂ · (1-x) Li ₂ M′O ₃ , wherein M is one At least one trivalent metal ion, at least one metal ion is Mn ^{+ 3} , Co ^{+ 3} or Ni ^{+ 3} , and M 'represents at least one metal ion having an average valence of +4, wherein 0 <x <1 Lithium ion secondary battery. The lithium ion secondary battery of claim 2, wherein the second lithium intercalation composition further comprises from about 0.1 mol% to about 10 mol% metal fluoride as a coating. The lithium ion secondary battery of claim 1, wherein the positive electrode comprises about 0.1-5% by weight of an electrically conductive material separately from the second lithium intercalation composition. The lithium ion secondary battery of claim 1, wherein the positive electrode comprises about 0.5 to 7.9 weight percent of a polymeric binder. The lithium ion secondary battery of claim 5, wherein the polymeric binder has an average molecular weight of at least about 800,000 atomic mass units. The lithium ion secondary battery of claim 1, wherein the negative electrode has a thickness of about 65 microns to about 200 microns on the cross section of the current collector. The lithium ion secondary battery of claim 1, wherein the battery has a discharge energy density of at least about 250 Wh / kg to 550 Wh / kg. The lithium ion secondary battery of claim 1 having a volumetric discharge energy density of at least about 550 Wh / l. A lithium ion secondary battery comprising a positive electrode, a negative electrode including a first lithium intercalation composition, and a separator between the positive electrode and the negative electrode,
The positive electrode comprises at least about 92% by weight of positive electrode active material, from about 0.1 to 5% by weight of electrically conductive material and from about 0.5 to 7.9% by weight of a polymeric binder;
The positive electrode active material comprises a second lithium intercalating composition represented by the formula xLiMO ₂ · (1-x) Li ₂ M'O ₃ , wherein M is one or more trivalent metal ions and one or more metal ions is Mn ^{+ 3} , Co ⁺³ or Ni ⁺³ , M 'represents one or more metal ions having an average valence of +4, 0 <x <1, and any fluorine dopant is substituted with about 1 atomic percent or less oxygen in the formula Can do it;
The density of the positive electrode is about 2.5 g / ㎖ or more lithium ion secondary battery. The composition of claim 10, wherein the second lithium intercalation composition is represented by the formula Li _{1 + x} Ni _α Mn _β Co _γ O ₂ , wherein x ranges from about 0.05 to about 0.25 and α is from about 0.1 to about 0.4 In the range from about 0.4 to about 0.65, and γ in the range from about 0.05 to about 0.3. The lithium ion secondary battery of claim 10, wherein the positive electrode material further comprises from about 0.1 mol% to about 10 mol% metal fluoride as a coating. The lithium ion secondary battery of claim 12, wherein the metal fluoride comprises AlF ₃ . The composition of claim 10, wherein the second lithium intercalation composition is represented by the formula Li _{1 + x} Ni _α Mn _β Co _γ M ″ _δ O _{2 -z / 2} F _z , wherein x ranges from about 0.05 to about 0.25 α is in the range of about 0.1 to about 0.4, β is in the range of about 0.4 to about 0.65, γ is in the range of about 0.05 to about 0.3, δ is in the range of about 0 to about 0.1, and z is about 0 to In the range of about 0.1 and M ″ is Mg, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, or a combination thereof. The lithium ion secondary battery of claim 10, wherein the negative electrode comprises graphite, synthetic graphite, hard carbon, graphite coated metal foil, coke, or a combination thereof. The lithium ion secondary battery of claim 10, wherein the separator comprises polyethylene, polypropylene, ceramic-polymer composite, or a combination thereof. The lithium ion secondary battery of claim 10, wherein the separator comprises a polyethylene-polypropylene-polyethylene triple layer membrane. The lithium ion secondary battery of claim 10, wherein the electrically conductive material comprises graphite, carbon black, metal powder, metal fiber, or a combination thereof. The polymer binder according to claim 10, wherein the polymer binder is polyvinylidene fluoride (PVDF), polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylate, ethylene- (propylene-diene monomer) copolymer (EPDM), And mixtures and copolymers thereof. The lithium ion secondary battery of claim 10, wherein the battery comprises a plurality of electrodes each having a polarity separated by a separator in the casing. The lithium ion secondary battery of claim 20, wherein the electrodes and separators are stacked, jelly-rolled, or folded inside the casing. The lithium ion secondary battery of claim 20, wherein the casing comprises a polymer film, a metal foil, a metal can, or a combination thereof. The lithium ion secondary battery of claim 20 wherein the casing is prismatic. The lithium ion secondary battery of claim 20, wherein the casing is cylindrical in shape. The lithium ion secondary battery of claim 10, wherein the battery has a discharge energy density of at least about 250 Wh / kg when discharged from 4.6 V to 2.0 V. 12. A method of forming a lithium ion secondary battery,
The method includes assembling a positive electrode, a negative electrode, and a separator to form a battery having a discharge energy density of about 240 Wh / kg or more,
The separator is inserted between the positive electrode and the negative electrode,
The positive electrode comprises a positive electrode active material and a binder, the positive electrode active material comprises a lithium intercalation composition,
And the density of the anode is at least about 2.5 g / ml. Of claim 26, wherein the positive electrode was formed by coating a positive electrode active material of a positive electrode using a binder to a current collector, a positive electrode comprising a positive active material of at least about 92% by weight, the lithium intercalation composition formula xLiMO ₂ · Represented by (1-x) Li ₂ M'O ₃ , where M is one or more trivalent metal ions, one or more metal ions is Mn ⁺³ , Co ⁺³ or Ni ⁺³ , and M 'is +4 At least one metal ion having an average valence of 0 <x <1. 28. The method of claim 27, wherein the current collector comprises a metal foil, a metal grid, or an expanded metal. The method of claim 27, wherein the current collector comprises nickel, aluminum, stainless steel, copper, or a combination thereof. 27. The method of claim 26, wherein the anode further comprises about 0.1-5 weight percent electrically conductive material. 27. The method of claim 26, wherein the positive electrode comprises about 0.5 to 7.9 weight percent polymer binder. The method of claim 26, wherein the binder is a polymer having an average molecular weight of at least about 800,000 atomic weight units. 27. The method of claim 26, wherein the negative electrode has a thickness of about 65 microns to about 200 microns on the cross section of the current collector. 27. The method of claim 26, wherein the battery has a discharge energy density of at least about 250 Wh / kg when discharged from 4.6 V to 2.0 V. A lithium ion secondary battery comprising a positive electrode, a negative electrode including a first lithium intercalation composition, and a separator between the positive electrode and the negative electrode,
The positive electrode comprises at least about 92% by weight of the positive electrode active material, about 0.1 to 5% by weight of the electrically conductive material and about 0.5 to 7.9% by weight of the polymeric binder including PVDF;
And the polymeric binder has an average molecular weight of at least about 800,000 atomic weight units.

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